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RegulatoryStatus:
Atrazine has been classified as a Restricted Use Pesticide (RUP)
due to its potential for groundwater contamination [2]. RUPs may
be purchased and used only by certified applicators. Atrazine is
toxicity class III - slightly toxic. In November, 1994, the EPA
initiated a Special Review which could result in use restrictions
or cancellation of atrazine if health data warrant such action.
Products containing atrazine must the Signal Word CAUTION.

Chemical Class:
triazine

Introduction:
Atrazine is a selective triazine herbicide used to control
broadleaf and grassy weeds in corn, sorghum, sugarcane,
pineapple, christmas trees, and other crops, and in conifer
reforestation plantings. It is also used as a nonselective
herbicide on non-cropped industrial lands and on fallow lands.
Over 64 million acres of cropland were treated with atrazine in
the U.S. in 1990. It is available as dry flowable, flowable
liquid, liquid, water dispersible granular, and wettable powder
formulations.

Formulation: It is
available as dry flowable, flowable liquid, liquid, water
dispersible granular, and wettable powder formulations.

Toxicological Effects:

Acute toxicity: Atrazine is slightly to
moderately toxic to humans and other animals. It can be
absorbed orally, dermally, and by inhalation. Symptoms of
poisoning include abdominal pain, diarrhea and vomiting,
eye irritation, irritation of mucous membranes, and skin
reactions [3]. At very high doses, rats show excitation
followed by depression, slowed breathing, incoordination,
muscle spasms, and hypothermia [3]. After consuming a
large oral dose, rats exhibit muscular weakness,
hypoactivity, breathing difficulty, prostration,
convulsions, and death [16]. Atrazine is a mild skin
irritant. Rashes associated with exposure have been
reported. The oral LD50 for atrazine is 3090 mg/kg in
rats, 1750 mg/kg in mice, 750 mg/kg in rabbits, and 1000
mg/kg in hamsters. The dermal LD50 in rabbits is 7500
mg/kg and greater than 3000 mg/kg in rats [15,16]. The
1-hour inhalation LC50 is greater than 0.7 mg/L in rats.
The 4-hour inhalation LC50 is 5.2 mg/L in rats [3,6].

Chronic toxicity: Some 40% of rats
receiving oral doses of 20 mg/kg/day for 6 months died
with signs of respiratory distress and paralysis of the
limbs. Structural and chemical changes in the brain,
heart, liver, lungs, kidney, ovaries, and endocrine
organs were observed [3,16]. Rats fed 5 or 25 mg/kg/day
of atrazine for 6 months exhibited growth retardation. In
a 2-year study with dogs, 7.5 mg/kg/day caused decreased
food intake and increased heart and liver weights. At 75
mg/kg/day, there were decreases in food intake and body
weight gain, increased adrenal weight, lowered blood cell
counts, and occasional tremors or stiffness in the rear
limbs [3].

Reproductive effects: Dietary doses of
atrazine given to rats on days 3, 6 and 9 of gestation up
to about 50 mg/kg/day caused no adverse reproductive
effects [3].

Teratogenic effects: Atrazine does not
appear to be teratogenic. In mice, atrazine did not cause
abnormalities in fetuses whose dams were given doses of
46.4 mg/kg/day during days 6 through 14 of gestation [3].

Mutagenic effects: The weight of
evidence from more than 50 studies indicates that
atrazine is not mutagenic [3].

Carcinogenic effects: Atrazine did not
cause tumors when mice were given oral doses of 21.5
mg/kg/day from age 1 to 4 weeks, followed by dietary
doses of 82 mg/kg for an additional 17 months. However,
mammary tumors were observed in rats after lifetime
administration of high doses of atrazine [3]. Thus,
available data regarding atrazine's carcinogenic
potential are inconclusive.

Organ toxicity: Lethal doses of atrazine
in test animals have caused congestion and/or
hemorrhaging to the lungs, kidneys, liver, spleen, brain,
and heart [3]. Long-term consumption of high levels of
atrazine has caused tremors, changes in organ weights,
and damage to the liver and heart [3].

Fate in humans and animals: Atrazine is
readily absorbed through the gastrointestinal tract. When
a single dose of 0.53 mg atrazine was administered to
rats by gavage, 20% of the dose was excreted in the feces
within 72 hours. The other 80% was absorbed across the
lining of the gastrointestinal tract into the
bloodstream. After 72 hours, 65% was eliminated in the
urine and 15% was retained in body tissues, mainly in the
liver, kidneys, and lungs [3].

Ecological Effects:

Effects on birds: Atrazine is
practically nontoxic to birds. The LD50 is greater than
2000 mg/kg in mallard ducks. At dietary doses of 5000
ppm, no effect was observed in bobwhite quail and
ring-necked pheasants [15,16].

Effects on aquatic organisms: Atrazine
is slightly toxic to fish and other aquatic life.
Atrazine has a low level of bioaccumulation in fish. In
whitefish, atrazine accumulates in the brain, gall
bladder, liver, and gut [16].

Effects on other organisms: Atrazine is
not toxic to bees [16].

Environmental Fate:

Breakdown in soil and groundwater:
Atrazine is highly persistent in soil. Chemical
hydrolysis, followed by degradation by soil
microorganisms, accounts for most of the breakdown of
atrazine. Hydrolysis is rapid in acidic or basic
environments, but is slower at neutral pHs. Addition of
organic material increases the rate of hydrolysis.
Atrazine can persist for longer than 1 year under dry or
cold conditions [21]. Atrazine is moderately to highly
mobile in soils with low clay or organic matter content.
Because it does not adsorb strongly to soil particles and
has a lengthy half-life (60 to >100 days), it has a
high potential for groundwater contamination despite its
moderate solubility in water [20]. Atrazine is the second
most common pesticide found in private wells and in
community wells [16]. Trace amounts have been found in
drinking water samples and in groundwater samples in a
number of states [23,21]. A 5-year survey of drinking
water wells detected atrazine in an estimated 1.7% of
community water systems and 0.7% of rural domestic wells
nationwide. Levels detected in rural domestic wells
sometimes exceeded the MCL [23]. The recently completed
National Survey of Pesticides in Drinking Water found
atrazine in nearly 1% of all of the wells tested [23].

Breakdown in water: Atrazine is
moderately soluble in water. Chemical hydrolysis,
followed by biodegradation, may be the most important
route of disappearance from aquatic environments.
Hydrolysis is rapid under acidic or basic conditions, but
is slower at neutral pHs. Atrazine is not expected to
strongly adsorb to sediments. Bioconcentration and
volatilization of atrazine are not environmentally
important [21]. Atrazine has been detected in each of 146
water samples collected at 8 locations from the
Mississippi, Ohio and Missouri Rivers and their
tributaries. For several weeks, 27% of these samples
contained atrazine concentrations above the EPA's maximum
contaminant level (MCL) [24].

Breakdown in vegetation: Atrazine is
absorbed by plants mainly through the roots, but also
through the foliage. Once absorbed, it is translocated
upward and accumulates in the growing tips and the new
leaves of the plant. In susceptible plant species,
atrazine inhibits photosynthesis. In tolerant plants, it
is metabolized [6]. Most crops can be planted 1 year
after application of atrazine. Atrazine increases the
uptake of arsenic by treated plants [16].

References for the information in this PIP can be found in
Reference List Number 8

DISCLAIMER: The
information in this profile does not in any way replace or
supersede the information on the pesticide product labeling or
other regulatory requirements. Please refer to the pesticide
product labeling.